Sub-mezzanine structure for printed circuit card assemblies

ABSTRACT

A method of assembling and configuring multiple mezzanine cards on a carrier card is disclosed. The method includes the establishing an I/O profile that represents the I/O configuration of a mezzanine card. The I/O of the mezzanine card is not enabled unless the I/O profile matches a known value stored on the carrier card. In this way, the electronic circuitry is protected if an incorrect mezzanine card is connected to the carrier card.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit to U.S. Provisional Application Ser. No.60/822,571 filed on Aug. 16, 2006, the disclosure of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a printed circuit (PC) card assembly.More particularly, the present invention relates to a mezzanine circuitboard that is mounted to a carrier circuit board.

BACKGROUND

Requirements for input/output (I/O) pin connections between circuitcards and motherboards often exceed the available circuit card edgelength and exceed the maximum available connector pin density. Onesolution to this problem is the use of a supplemental card portioncalled a “mezzanine” card (sometimes referred to as a “daughter” card)that is mounted to the main circuit card (referred to generically as thecarrier card) in order to provide one or more additional connectors andadditional I/O pins. Such mezzanine cards are useful to provideadditional functionality to a main circuit card, typically in the formof increased I/O capability. This increased I/O capability serves avariety of applications such as data acquisition and communication justto name a few. Mezzanine cards provide a convenience for configuring acarrier card. For a given carrier card with a suitable FieldProgrammable Gate Array (FPGA), there can be numerous configurations ofattachable mezzanine cards that can satisfy a wide application scope.Modules can be digital, analog, communication, etc. and there can be a“mix” of such modules on a single carrier card. As applications continueto demand increased data processing and communications, while retainingcompact physical size, mezzanine cards are commonly used to meet thesedemands.

However, the use of mezzanine cards creates new design issues becausethe connectors on the main circuit card and the mezzanine card must bespaced at a carefully controlled distance so that the circuit card andmezzanine card connectors can be mated properly with the matingconnectors that are positioned on the main circuit card. The spacingbetween the connectors on the main circuit card and the mezzanine cardis relatively small. Since electronic devices on the mezzanine card giveoff heat during operation, the confined area between the main circuitcard and the mezzanine card also makes heat dissipation an issue.Furthermore, since the applications for which the mezzanine cards areused often are harsh environments with considerable mechanicalvibration, there is also an issue regarding the robustness of themechanical mounting of the mezzanine card to the main circuit card.Therefore, it is desirable to have an improved mezzanine structure forPC assemblies.

SUMMARY OF THE INVENTION

A novel arrangement and assembly method are disclosed in order to moreefficiently arrange mezzanine cards on a carrier card. The carrier cardmay conform to any one of a number of standards, including, but notlimited to, PCI Mezzanine Card (PMC), AMC, CMC, XMC, CompactPCI, PC104,PCI, PCI Express, and VME. One preferred embodiment of the mezzaninecard of the present invention has a substantially square form factor, ofabout 1.25 inches on each side. This form factor provides the advantagesof making efficient use of board space, and allowing up to four suchmezzanine cards to be placed on a PMC, and still comply with thedimensional requirements of both the IEEE 1386 and VITA 20 standards.The mezzanine card of the present invention is a “single connector”mezzanine card. A single connector is used on the mezzanine card tosimplify alignment issues, thereby providing more efficient assembly.The mezzanine card is mounted on standoffs to facilitate attachment ofsemiconductor devices (chips) on both sides of the mezzanine card. In apreferred embodiment, the single connector is a high density 2millimeter stacking connector. The standoffs are preferably secured inplace on the carrier card with solder, and then fasteners, such asscrews having an adhesive substance applied to them are used to fastenthe mezzanine board to the carrier card. As an alternative, or inaddition to the adhesive, lock washers may be used, so long as thedesired dimensional requirements are not exceeded.

Due to dimensional requirements of IEEE 1386, the standoffs are fairlylow, leaving little space between the mezzanine card and the carriercard assembly. Therefore, heat dissipation is an area of concern whenusing mezzanine cards. The present invention optionally providesadditional heat dissipation via a conformal heat conductive materialthat is placed between the carrier card assembly and the mezzanine card.The use of the conformal heat conductive material depends on theapplication. In a low-power application, air cooling may be sufficient.However, high-power applications may require the additional heatdissipation achieved with the conformal heat conductive material.

In an alternate embodiment, the carrier can actually be anothermezzanine card, in which case, the mezzanine card of the presentinvention acts as a so called “sub-mezzanine” card. However, it ispossible to use the mezzanine card of the present invention directlywith a main circuit board configured with the proper connections withoutdeparting from the scope of the present invention.

The present invention provides the advantages of increasing the I/Oflexibility of a carrier card such as a PMC, provides acceptable heatdissipation within a small physical form factor, and provides a securemechanical mount of the mezzanine card to the carrier card. Another keyadvantage of the present invention is the ability to support multiplemezzanine cards on a single PMC. This provides the flexibility ofconfiguring multiple functions on a single carrier card.

The present invention also provides the advantage of identifying thetype of mezzanine card present, comprising the steps of reading anidentification string with a processor or FPGA on the carrier card. Theidentification string includes an I/O profile as part of its data. ThisI/O profile contains information about the status of each I/O pin on themezzanine card, including whether a particular I/O pin is to be used asan input, output, or bi-directional. This I/O profile is compared with aconstant value (reference data) stored in the FPGA or memory on thecarrier card. Only if the I/O profile matches the constant value, willthe I/O pins be enabled (transitioned from tri-stated to active) on themezzanine card. If the I/O profile does not match, the I/O pins on themezzanine card are tri-stated, thereby protecting the mezzanine cardcircuitry. These advantages, and others, will be apparent from thedetailed description and drawings that follow.

ASPECTS OF THE INVENTION

1. This aspect of the invention is a circuit card assembly comprising:

a carrier card (300);

at least one single connector mezzanine card (100);

wherein the single connector mezzanine card makes electrical contactwith the carrier card via a connector (108) on the mezzanine card thatis in electrical contact with a corresponding connector (304) on thecarrier card, the carrier card having a plurality of mounting holes(312), and a plurality of standoffs (308), each mounting hole (312)having a corresponding standoff (308) aligned with it, the singleconnector mezzanine card (100) having a plurality of mounting holes(104, 106) aligned with the standoffs (308), and having screws (306)having a threaded shaft (602) wherein the lower portion of the threadedshaft (602) has adhesive (604) applied to it, thereby securely fasteningthe mezzanine card (100) to the carrier card (300).

2. This aspect is the circuit card assembly of aspect 1, furthercomprising a layer of conformal heat conductive material (702) isapplied on the carrier card 300, underneath mezzanine card 100.

3. This aspect is a method for assembling a single connector mezzaninecard to a carrier card, comprising the steps of;

Aligning standoffs (308) with mounting holes (312) of a carrier card(300), and soldering the standoffs to the carrier card, placing a singleconnector mezzanine card (100) onto the carrier card such that mountingholes (104,106) of the mezzanine card are aligned with the standoffs,and applying adhesive (604) to the lower portion of the threaded shaft(602) of screws (306), and fastening the mezzanine card to the carriercard with the screws.

4. This aspect is a method for the carrier card to identify the type ofmezzanine card present, comprising the steps of reading anidentification string transmitted by the mezzanine card, and receivingthe identification string with a processor or FPGA on the carrier card,the processor or FPGA using the identification string as a means ofestablishing signal directionality between the FPGA on the carrier cardand the mezzanine card I/O.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of the connector side of a preferred embodimentof the mezzanine card of the present invention.

FIG. 2 shows a plan view of the non-connector side of the embodimentshown in FIG. 1.

FIG. 3 shows a plan view of an exemplary carrier card of the presentinvention.

FIGS. 4A and 4B show plan views of exemplary carrier cards utilizingmultiple mezzanine cards of the present invention.

FIGS. 5A and 5B show side views of a mezzanine card mounted to a carriercard.

FIG. 6 is an exploded view of a mezzanine card mounted to a carriercard.

FIG. 7 shows a side view of a mezzanine card mounted to a carrier cardwith a conformal heat conductive material.

FIG. 8 shows another embodiment of a carrier card of the presentinvention.

FIG. 9 shows a logical view of a preferred embodiment of the presentinvention.

FIG. 10 shows a sequence of steps to generate an identification string.

FIG. 11 shows the flowchart of steps performed during moduleidentification.

FIG. 12 shows an exemplary ID string 1200 containing various datafields.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a plan view of the connector side of a preferred embodimentof the single connector mezzanine card 100 of the present invention.Mezzanine card 100 comprises printed circuit card 102, which hasmezzanine connector 108 attached thereto. In a preferred embodiment,connector 108 is a high density 2 millimeter stacking 80-contactconnector.

Using a single connector 108 provides an advantage over previous designsthat have employed multiple connectors. When multiple connectors areused, there is increased chance for tolerance build-up that causesalignment issues, and prevents mounting of the mezzanine card. Thepresent invention overcomes these problems by using a single highdensity connector. In one embodiment, the single high density connectoris not keyed. Using a non-keyed connector reduces the risk of damage dueto someone inadvertently trying to force the two parts of the keyedconnector together in the wrong position. Therefore, in order to reducethe risk of incorrect attachment, the single high density connector 108is purposely placed off-center within the mezzanine card 100. By havingan offset mezzanine connector, it becomes noticeable when the mezzaninecard 100 is inserted incorrectly, since the mezzanine mounting holes 104and 106 of the mezzanine card 100 will not line up with mounting holes312 of the carrier card 300.

Mezzanine card 100 has a plurality of mounting holes. In a preferredembodiment, two mezzanine mounting holes are positioned at oppositecorners, indicated as 104 and 106. Mezzanine card 100 accommodatesmultiple integrated circuit devices (hereinafter referred to as“chips”). In the embodiment shown, eight chips, referenced as U2 throughU9 are shown.

FIG. 2 shows a plan view of the non-connector side of the mezzanine card100 shown in FIG. 1. Additional devices may be placed on this side. Inthe embodiment shown, two devices, indicated as U1 and U10 are shown. Ina preferred embodiment, one of the devices (chips) present on themezzanine card 100 is a microcontroller. The microcontroller is used forgenerating and transmitting an identification string. Thisidentification string can be used by the carrier card to identify anattached mezzanine card. More particularly, the identification stringcontains an I/O profile for the mezzanine card 100. This I/O profilecontains data representative of the I/O status (e.g. input, output, orbi-directional) for each I/O signal on the mezzanine card 100.

FIG. 3 and FIG. 4A show plan views of an exemplary carrier card 300 ofthe present invention. The carrier card 300 comprises a printed circuitcard 302, with a plurality of devices mounted thereon. The embodimentshown in FIG. 3 is a PCI Mezzanine Card (PMC). PMC cards are generallyknown in the art. However, the PMC card of the present invention has aunique arrangement of four carrier card connectors, each indicated as304. Each carrier card connector 304 mates with mezzanine connector 108on a mezzanine card 100, forming a connector pair. The arrangement ofconnectors 304 allow up to four mezzanine cards 100 to be mounted on PMCcarrier card 300, as is shown in FIG. 4 Note that in this case, thecarrier card 300 is itself a mezzanine card, making mezzanine card 100 asub-mezzanine card. However, for consistent terminology, carrier cardrefers to the circuit card on which mezzanine card 100 is mounted. Theterm “mezzanine” card is used to refer to the smaller “daughter” card,regardless of whether the carrier card is another mezzanine card, or amain circuit card.

FIG. 4B shows an alternative embodiment of the carrier card 400 of thepresent invention. In this embodiment, the carrier card 400 adheres tothe VME standard, and can support up to twelve mezzanine cards 100.

FIG. 5A shows a side view of a mezzanine card 100 mounted to a carriercard 300 as viewed from position A of FIG. 1. The mezzanine card 100 hasa plurality of chips installed on it, referred to generally as UX forthe chips on the non-connector side of the mezzanine card 100, and UYfor the chips on the connector side of the mezzanine card 100. Forclarity of the drawing, not all chips are marked with a reference.Carrier card 300 has a plurality of carrier card mounting holes 312aligned with holes 104 and 106 of mezzanine card 100. In a preferredembodiment, standoffs 308 are placed on carrier card 300 during theboard population process, and then soldered on to permanently mountthem. In a preferred embodiment, standoff 308 is a 2 millimeterstandoff, such as that manufactured by PennEngineering of Danboro, Pa.,USA. Standoffs 308 are positioned on carrier card 300 aligned withmounting holes 312. Mezzanine card 100 is then placed on to carrier card300 such that the connector side of mezzanine card 100 (shown in FIG. 1)faces the carrier card 300. Mezzanine card connector 108 makeselectrical contact with carrier card connector 304. A plurality ofscrews, indicated as 306, mechanically fasten mezzanine card 100 tocarrier card 300.

The type and number of chips shown are dependent on the specificapplication. It is preferable that low profile chips, such as SmallOutline Integrated Circuits (SOICs) are used, to remain within theacceptable physical size limits. For example, in the case of the IEEE1386 specification, the cumulative height of the mezzanine board(including mounted components) must be less than 4.7 millimeters fromthe surface of the carrier card.

FIG. 5B shows the key dimensions that are considered to be within limitsof the cumulative height Hc. To remain within the cumulative heightlimit, the mezzanine card thickness Tm of the mezzanine card 100 must besmall enough such that Hc, which is the sum of standoff height Hs (Hs isapproximately 2 millimeters in a preferred embodiment, thereby allowingenough space to handle standard height SOIC devices), mezzanine cardthickness Tm, and device height Hd (in a preferred embodiment, Hd has amaximum value of 1.9 millimeters) is less than the cumulative heightlimit, which is 4.7 millimeters in the case of the IEEE 1386specification. In a preferred embodiment, the mezzanine card thicknessTm is approximately 0.8 millimeters.

FIG. 6 is an exploded view of a mezzanine card 100 mounted to a carriercard 300 as viewed from position A of FIG. 1. In this view, threadedshaft 602 of screw 306 is shown. As part of the assembly process, alayer of adhesive 604 is applied to the lower portion of shaft 602. Thescrew 306 is then fastened onto carrier card 302 shortly thereafter,before the adhesive sets. After the screws 306 are in place, theadhesive then sets, securing the screws 306, and thus mezzanine card100, to the carrier card 300. Using this method provides increasedrobustness in a harsh environment, such as in an industrial application,where the carrier card may be subject to considerable vibration. Whileit is possible to use lock washers to prevent the screws 306 fromloosening after assembly, the adhesive provides an advantage over usinga lock washer in that the overall height of the mezzanine card does notincrease when an adhesive is used, whereas lock washers do increase theheight. In an exemplary embodiment, the adhesive 604 is LOCTITE 222MS,manufactured by Henkel Consumer Adhesives, of Avon, Ohio, USA. LOCTITE222MS is a non-permanent adhesive. It serves to secure screws 306 andprevent them from loosening due to mechanical vibration and the like.However, since adhesive 604 is non-permanent, the screws 306 may beloosened with a screwdriver, so that the mezzanine card 100 can beremoved and replaced as necessary.

FIG. 7 shows a side view of a mezzanine card 100 mounted to a carriercard 300 as viewed from position B of FIG. 1. In this figure, optionalconformal heat conductive material 702 is shown. A layer of conformalheat conductive material 702 is applied on the carrier card 300,underneath mezzanine card 100. The conformal heat conductive material702 conforms to the chips (referenced as UY) on the connector side ofmezzanine card 100. The conformal heat conductive material 702 is mosttypically used on VITA 20 Conduction Cooled PMC carrier cards. In alow-power application, convection or forced air cooling may besufficient. However, when the devices give off sufficient heat,conformal heat conductive material 702 can optionally be used to improveheat dissipation. The conformal heat conductive material is anelectrically isolating material, preferably having a thermalconductivity of at least 1.0 W/mK (Watt per meter Kelvin), a dielectricbreakdown voltage greater than about 6,000 volts AC, and a dielectricconstant greater than about 5.4, as measured by ASTM D150. The conformalheat conductive material typically is in sheet form. In one embodiment,the Young's Modulus of the conformal heat conductive material ispreferably about 55 kPA, and the density (g/cc) is about 1.6. In anexemplary embodiment, conformal heat conductive material 702 is from theGap Pad VO Ultra Soft product family, which is manufactured by BergquistCompany of Chanhassen Minn., USA. In an exemplary embodiment, partnumber GPVOUS-0.100-AC-0816 is used. However, when practicing thepresent invention, there may be some variation in the part number due todifferent thickness requirements from one application to the next.

FIG. 8 shows another embodiment of a carrier card of the presentinvention. In this case, copper ground plane 808 is optionally presenton the surface of PMC carrier card 800 in the proximal area of eachcarrier card connector 304. For the sake of clarity, not all groundplanes are indicated with reference numbers in this figure. The presenceof the copper ground plane 808 is essential when the optional conformalheat conductive method of the present invention is used. This is shownin FIG. 7. If the conformal heat conductive method of the presentinvention is used, conformal heat conductive material (702 in FIG. 7)makes contact with the copper ground plane 808. The heat is transferredto copper ground plane 808, and away from the electronic circuitry.Preferably, side rails (not shown) divert the heat from the copperground plane 808.

FIG. 9 shows a logical view of a preferred embodiment of the presentinvention. PCI bus 900 is connected to PCI bus interface 902. PCI businterface 902 provides the necessary circuitry to communicate with FPGA(Field Programmable Gate Array) 904. The PCI bus interface is well knownin the art. The FPGA 904 communicates with one or more mezzanine cards,indicated here as 906A-906D. Note that while an FPGA is used tointerface with the PCI bus interface in this embodiment, it is possibleto use other technologies, such as a microcontroller, to perform thisfunction, without departing from the scope of the present invention.Each mezzanine card 906A-906D is mechanically similar to mezzanine card100. The mezzanine cards 906A-906D are electrically connected to I/O(input/output) connector 909 through I/O Signals 907. The references906A-906D refer to specific instances of a mezzanine card. Eachmezzanine card can have different electronics to perform a differentfunction. For example, mezzanine card 906A may provide signalconditioning for serial communications (e.g. RS-232) and/or parallelcommunications (e.g. IEEE-1284), mezzanine card 906B may provide signalconditioning for analog signal acquisition, mezzanine card 906C mayprovide signal conditioning for digital I/O, and mezzanine card 906D mayprovide for memory storage, provide for on-board sensors such astemperature sensors, accelerometers, or other transducers, or performyet another function. While four mezzanine cards are shown in thisembodiment, it is possible to have more or less without departing fromthe scope of the present invention. In general, FPGA 904 provides thelogic operations necessary for a particular function, and the signalconditioning is performed on the mezzanine cards 906A-906D. Not allmezzanine cards need be present during use. For example, if the userdesired to configure a carrier card with only two functions, then onlytwo mezzanine cards would be used.

In this embodiment, each mezzanine card 906A-906D has a microcontroller(not shown) installed therein to transmit an identification string. Inan exemplary embodiment, the microcontroller is a PIC10F200 or similar,manufactured by Microchip Technology Inc., of Chandler, Ariz., USA.

FIG. 10 shows a sequence of steps performed by the PIC10F200 orequivalent to generate an identification string, hereinafter referred toas an ID string. The ID string is a sequence of data that isperiodically retransmitted. The FPGA reads the ID string, and canidentify the type of mezzanine card that has been inserted into thecarrier card. In a preferred embodiment, the data is pulse widthmodulated, wherein a zero bit is one pulse width unit, a one bit is twopulse width units, and a sync pulse is three pulse width units.

In step 1002, a sync pulse is sent to the FPGA. This indicates the startof the data sequence. In step 1004, the part number data is sent. Instep 1006 a serial number is sent. In step 1008, a revision date issent. In step 1010 a manufacturing date is sent. In step 1011 an I/Oprofile is sent. The I/O profile is representative of the configurationof each I/O signal. In step 1012 optional data is sent. In step 1014 achecksum of the previous data is sent. The checksum is optionally usedby the FPGA to verify the integrity of the received data. After aperiodic delay, the process proceeds to step 1002, and the ID string isretransmitted at a predetermined interval (e.g. every 250 milliseconds).

FIG. 11 shows the flowchart of steps performed by the FPGA during moduleidentification. In general, when a mezzanine card is inserted into thesocket on the carrier card, the FPGA 904 provides power to the mezzaninecards 906A-906D, but does not enable the I/O signals 907 of themezzanine cards 906A-906D. The FPGA 904 reads the ID string and candetermine if a particular mezzanine card is designed to work with thatcarrier card. In step 1102, the ID string is received by the FPGA 904.In step 1104, the FPGA 904 compares the received ID string to aninternally stored table of ID strings (not shown). The I/O profile,which contains the configuration data for the I/O signals on themezzanine cards 906A-906D, is compared to a value stored internally inthe FPGA on the carrier card 300. If the I/O profile for a givenmezzanine card matches the value internally stored by the FPGA 904, thenthe I/O signals 907 of the mezzanine card are enabled in step 1106.Various other parameters, such as serial number, revision date, andmanufacturing date may optionally be compared. If the compared data doesnot match, then the I/O signals 907 remain disabled (tri-stated). Thisprovides protection of the electronics if an incorrect mezzanine card isinadvertently placed in the wrong carrier card.

FIG. 12 shows an exemplary ID string 1200 containing various datafields. In an exemplary embodiment, the module part number 1202, serialnumber 1204, revision date 1206, and manufacturing date 1208 are storedas 3 byte BCD encoded data. The I/O profile 1210 is stored as sevenbytes of data. Two bits of data are used to represent the configurationsetting of each I/O pin. In this embodiment, a two bit value of 00denotes an output from the mezzanine card, a two bit value of 01 denotesan input to the mezzanine card, and a two bit value of 10 denotes abi-directional signal. Those skilled in the art will recognize thatother values may be used to represent the various I/O states withoutdeparting from the scope of the present invention. Optional data 1212may contain additional information about the module, referred to as“Module Specific Data.” The checksum 1214 is optionally used to verifythe integrity of the received data.

As can be understood by one of ordinary skill in this art, the presentinvention provides increased I/O flexibility, acceptable heatdissipation within a small physical form factor, and provides a securemechanical mounting. Furthermore, a method of modular mezzanine cards isdisclosed. The mezzanine cards identify themselves to a processor on thecarrier card, and identify their I/O profile to the carrier card whichensures the mezzanine cards are the proper type for the carrier cardbefore enabling the I/O signals of the mezzanine card, therebyminimizing the risk of damage due to human error. Those of ordinaryskill in the art will recognize that the above description was simplyusing exemplary embodiments to illustrate the making and using of theinvention and, that other combinations are possible without departingfrom the scope of the present invention.

1. A circuit card assembly comprising: a carrier card; at least onesingle connector mezzanine card; wherein the single connector mezzaninecard makes electrical contact with the carrier card via a mezzanineconnector on the mezzanine card that is in electrical contact with acorresponding carrier card connector on the carrier card, and whereinthe mezzanine connector is offset from the center of the mezzanine card,the carrier card comprising a plurality of carrier card mounting holes,the mezzanine card having a plurality of mezzanine mounting holes, aplurality of standoffs disposed between the carrier card and themezzanine card, wherein each mezzanine mounting hole is configured inalignment with a corresponding standoff and a corresponding carrier cardmounting hole, and comprising a plurality of fasteners, and a means forsecuring each of the plurality of fasteners, each of the plurality offasteners disposed to traverse the corresponding standoff, and engage inthe corresponding carrier card mounting hole, thereby fastening themezzanine card to the carrier card.
 2. The circuit card assembly ofclaim 1, wherein the single connector mezzanine card has a substantiallysquare form factor.
 3. The circuit card assembly of claim 1, wherein thesingle connector mezzanine card has a substantially square form factorin the range of about 1 inch to about 1.25 inches on each side, therebyallowing up to four of the single connector mezzanine cards to bedisposed on the carrier card, thereby complying with the dimensionalrequirements of IEEE 1386 and VITA 20 standards.
 4. The circuit cardassembly of claim 1, wherein the plurality of standoffs is secured tothe carrier card with solder.
 5. The circuit card assembly of claim 3,wherein the mezzanine connector is a 2 millimeter stacking connector. 6.The circuit card assembly of claim 1, wherein the carrier card conformsto a standard selected from the group consisting of AMC, PMC, CMC, XMC,CompactPCI, PC/104, PCI, PCI Express, and VME.
 7. The circuit cardassembly of claim 1, wherein the single connector mezzanine cardcomprises a microcontroller, said microcontroller configured anddisposed to transmit an identification string.
 8. The circuit cardassembly of claim 7, wherein said identification string comprises an I/Oprofile.
 9. The circuit card assembly of claim 1, wherein the singleconnector mezzanine card is configured to perform a function selectedfrom the group consisting of analog signal I/O, serial communications,parallel communications, memory device, sensor, and digital I/O.
 10. Thecircuit card assembly of claim 1, wherein the carrier card furthercomprises a copper ground plane in the proximal area of each carriercard connector, and a layer of conformal heat conductive materialdisposed on the carrier card and contacting the copper ground plane. 11.The circuit card assembly of claim 1, wherein the plurality of fastenerscomprises a plurality of screws, each of the plurality of screws havinga threaded shaft, and wherein the means for securing each of theplurality of screws comprises a layer of adhesive on the threaded shaftof each of the plurality of screws.
 12. The circuit card assembly ofclaim 1, wherein the carrier card connector and mezzanine connector arenon-keyed.
 13. A method for configuring a circuit card assembly, saidcircuit card assembly comprising a carrier card and at least one singleconnector mezzanine card, the mezzanine card having at least one I/Opin, the method comprising the steps of: transmitting an identificationstring from the mezzanine card; receiving the identification string onthe carrier card; comparing the identification string with referencedata stored on the carrier card; and enabling I/O signals on themezzanine card if the identification string matches the reference data,thereby providing protection of the circuit card assembly if anincorrect mezzanine card is inadvertently placed on the carrier card.14. The method of claim 13, wherein the step of transmitting anidentification string further comprises transmitting an I/O profile,wherein said I/O profile contains status information for each I/O pin onthe mezzanine card.
 15. The method of claim 13, wherein the step oftransmitting an identification string further comprises transmitting amodule part number.
 16. The method of claim 13, wherein the step oftransmitting an identification string from the mezzanine card comprisesthe steps of: transmitting a sync pulse; transmitting a part number;transmitting a serial number; transmitting a revision date; transmittinga manufacturing date; transmitting an I/O profile; and transmitting achecksum.
 17. The method of claim 13, wherein the step of transmittingan identification string from the mezzanine card is repeatedperiodically at a predetermined interval.
 18. The method of claim 14,wherein the step of comparing the identification string with referencedata stored on the carrier card further comprises the step of comparingthe I/O profile in the identification string with an I/O profile storedon the carrier card.
 19. The method of claim 16, wherein the step oftransmitting an I/O profile comprises the step of transmitting a two bitvalue corresponding to a configuration setting of each I/O pin of themezzanine card.
 20. A circuit card assembly comprising: a carrier card;at least one single connector mezzanine card; wherein the singleconnector mezzanine card makes electrical contact with the carrier cardvia a mezzanine connector on the mezzanine card that is in electricalcontact with a corresponding carrier card connector on the carrier card,and wherein the mezzanine connector is offset from the center of themezzanine card, the carrier card comprising an FPGA configured anddisposed to receive an identification string from the mezzanine card andcompare said identification string with reference data stored on thecarrier card, said FPGA configured and disposed to enable I/O signals onthe mezzanine card if data contained within the identification stringmatches said reference data.